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Full text of "Text Book Of Mechanical Engineering"

Appendix II.

793

resulting product, basic steel, is the nearest  possible  thing to
metallic iron.     Finally, in the

Acid-
Bessemer
Process

Basic-
Bessemer
Process

Suitable for intermediate
pigs,  with,  say,  -2  to

Open-
Hearth
Process.

Silicon supplies
heat for conversion

Phosphorus supplies
heat

Heat supplied
artificially.

Phosphorus must
be low

Silicon must
be low

•5% Phosphorus.

and the Basic process is chiefly of value on the Continent, where
phosphoric ores abound.

P. 83. Temper of Steel, or the proportion of carbon to
suit it to a particular purpose. The following table is the result
of actual analyses of Siemens' steel, extending over some three
or four years, and may be looked on as reliably representing
present-day practice. It shows the gradual tendency to decrease
carbon percentage, except in regard to steel used for cutting tools :

TEMPER OF STEEL.

Castings

Forgings .

Chains.

Percentage of
Carbon,

•3 to -4

•25 to -3

'35

•15 to '18

Locomotive  wheel centres,

locomotive firebox girders,

marine stem frames, &c.
Crank   pins,   crank shafts,

connecting rods
Piston rods to stand wear

To weld well

Springs—laminated................................................    '4 to *6

Boilerplates—ordinary.............................................    '17 to '2

Boiler plates—"for welding   __•...................................    '15 to '17

Tool steel...............................................................  17

The percentage in Bessemer steel is somewhat lower, if the same
strength is to be retained. Wrought iron, also by analysis, con-
tains from "25 °/Q of carbon down to mere traces.

P. 84, Electro-deposited Copper.—Ever since the dis-
covery of electro-metallurgy it has been known that purer copper
could thus be obtained, but the metal proved insufficiently dense,
and very weak. These difficulties have been overcome by